Gearless drive method and means

ABSTRACT

A synchronous motor has a circular rotating pair of cylindrical pole pieces of claw tooth form connected with propulsion means such as a propeller, and is driven by interaction of magnetic fields produced by segmented modular stator and field windings peripherally situated at spaced locations about the pole pieces energized by polyphase alternating current at a frequency determined by the speed of rotation of the pole pieces relative to the stationary stator and field coils. An additional DC signal is applied to the field windings. For higher power requirements, the number of segmented stator and field coil units can be increased.

United States Patent mi Pierro 1 51 Jan. 2, 1973 54 GEARLESS DRIVEMETHOD AND 3,422,275 1/1969 Braikevitch et a] ..4l7/356 x MEANS1,764,388 6/1930 Buchet. ..l l5/l8 E 3,143,972 8/1964 Smith et al...417/356 1 lnvemo" John Pier", Inglewwd, Callf- 3,303,369 2/1967Erickson ..3l0/263 x 73 A N rth A ri R k ll l sslgnee me can 0c wecorpora Primary Examiner-William L. Freeh Assistant Examiner-Gregory LaPointe [22] Filed: May 11, 1970 Attorney-L. Lee Humphries 21 Appl. No.7:29,326 [57] ABSTRACT Related P' Data A synchronous motor has a circularrotating pair of [62] Division of Ser. No. 741,676, July 1, 1968, Pat.No. cylindrical P9 Pieces of claw 100th form connected 3 543 9 5 withpropulsion means such as a propeller, and is driven by interaction ofmagnetic fields produced by 52 US. Cl. ..417/356, 115/18 E, 810/263segmented modular stator and fi windings 51 1111. Cl.....F04b 17/00,F04b 35/04, B63h 21/26, peripherally Situated at Spaced locatwnsaboutthe I "02k 1/22 pole pieces energized by polyphase alternating current[58] Field of Search ..417/356- 310/68 263- at a frequency determined bythe speed 115/18 the pole pieces relative to the stationary stator andfield coils. An additional DC signal is applied to the field windings.For higher power requirements, the [56] References Clted number ofsegmented stator and field coil units can be UNITED STATES PATENTSincreased- 2,697,986 12/1954 Meagher, Jr. ..4l7/356 2 Claims, 5 DrawingFigures mzmmm 2 ma SHEET 1 OF 2 FIG. I

Fl ELD SUPPLY ROTOR FIG. 4

FREQUENCY CONVERTER COMMUTATOR ALTERNATOR STATOR ROTOR n-gRF GEARLESSDRIVE METHOD AND MEANS This application is a division of' applicationSer. No. 741,676 filed July 1, 1968, now US. Pat. No. 3,548,965 grantedDec. 22, 1970.

SUMMARY OF THE INVENTION DESCRIPTION OF DRAWINGS FIG. 1 shows anisolated perspective view of a portion of a motor incorporating theinventive principles in this case, I

FIG. 2 shows a general perspective view in cross-section showing apropulsion system for boats incorporating the drive motor structureshown in FIG. 1,

1 of field poles 24 and 26. Rotor 16 may be seen to inv 1 clude aplurality of elongated substantially parallel and FIG. 3 shows a generalperspective view of the structure from FIG. 2 mounted on a boat,

FIG. 4 shows an illustrative arrangement of circuitry for the motorshown in FIG. 1, and FIG. 5 is, a graphic representation of the fluxfield intensities associated with operation of the motor shown in FIG.1.

DETAILED DESCRIPTION Referring generally to the drawings describedaboveand particularly to FIG. 1, it may be seen that the invention inthis case contemplates a rotational synchronous motor generallydesignated by reference numeral 10 having stator means 12 cooperativelyrelated. with field pole means 14, both being in spaced relationship,from substantially cylindrical rotor means 16. Stator means 12 includesa laminated core 18 and stator conductor windings 20 and adapted toproduce a flux field passing through the center of core 18. Stator means12 is'located in spaced relationship to field pole means 14 so as not tobe magnetically coupled to the field polemeans. Both items 12 and 14 aresegmented I from rotor means 16 which is of cylindrical form having acurvature generally corresponding with the curvature spaced apartprojections 32 extending from a common support 34, and a correspondingplurality of projections 36 extending from a second common support 38,the stated projections from elements 3.4 and 38 being interdigitated asshown, for example, in FIG. 1. It will be understood by those skilled inthe art that items 32 and 34 constitute a first magnetic member, whileitems 36 and 38 together constitute a second magnetic 1 member. Bothforegoing members are supported in fixed relationship such as by rigidring 40 permanently joined thereto as seen from FIG. 1 whereby items 32,

34, 36, 38, and 40 effectively comprise a single unitary structural massrotatable about a center of rotation as described below. An air gap 42between each of the juxtaposed salient magnet projections 32 and 36 isof sufiicient length to substantially eliminate magnetic flux leakagebetween the stated projections during operation of motor 10. Ring 40 issuitably non-magnetic such as a nickel base alloy, plastic, ceramic, orthe like.

Referring to FIG. 1, it will be understood that a magnetic field iscreated by energization'of field excitation coil 28 from asuitablesource of direct current. The flux field thus created by coil 28'withincenter portion 30 of frame 22 will have a shape corresponding generallywith the shape of frame 22, and thus will be downwardly directed by poleportion 24 into rotor 16 at a localized area of support 38 or else oneof the projections 36. In either case, the fiux path passes through atleast a portion of the salient magnetic projections 36 and into thestator core 18 due to magnetic force resulting from energization offield coil 28. It will be portion of projection 32 and reaches supportelement units, not totally surrounding rotor '16. Field pole means 14has a frame 22 with suitably formed poles 24 and 26 and an excitationcoil 28 positioned around the center portion 30 of the frame. It will beunderstood that frame 22 and pole elements 24, 26 may assume othershapes differing from those illustrated. Moreover, field excitation coil28 may be replaced in some cases with one or more permanent magnets toprovide a field flux in a manner described hereinbelow. The foregoingelements and their operation are more fully disclosed in U. S- Pat.application No. 581,946 filed Sept. 26, 1966 with common inventorship,now U. S. Pat. No. 3,456,136." I

As seen from FIG. 1, field pole elements 24 and 26 are of substantiallyidentical shape and contour. Stator means 12 and field pole elements 24and 26 are spaced 34 and travels therethrough, thence reaching fieldpole portion26 and continuing tocenter portion 30 of frame 22, thuscompleting the field excitation circuit.

Referring more particularly to FIG.4, operation of motor 10 may be seento advantageously include a commutator 46 preferably of electromagnetictype, which functions to sense the tangential velocity of rotor 16relative to stationary stator and field means 12 and 14, respectively,and acts as a position transducer. Commutator 46 provides a speed andposition signal of rotor 16 to a frequency converter 48 which issupplied either polyphase electrical power from a conventional source ofalte'mating current such as alternator 50, or a source of direct currentpower (not. shown). When using alternating current, current is suppliedto frequency converter 48 at a particular predeterrnine frequency f,,.Frequency converter 48 receives the velocity and position signal fromcommutator 46 and automatically maintainsan applied stator frequency f,according to the relationship f, equals. kPN, where k is a constant ofproportionality, equals the number of g at the applied stator frequencyf,,. Frequency converter 48 applies the variable frequency input f, tostator means 12 of motor so that the stator means creates a travelingmagnetic wave which substantially matches the linear velocity of theflux field generated by field means 14. The foregoing conditions resultin a stator magnetic wave and a field magnetic wave which are stationarywith respect to each other and are separated by a displacement angle orphase angle delta (8). Propulsive force results from operation of motor10 because of the two stated fields attempting to align. The statormagnetic wave normally leads the field magnetic wave, resulting in thementioned force or thrust betweenstator means 12 and rotor 16 of motor10. The operative relationship between commutator 46 and frequencyconverter 48 is also adaptable to operate motor 10 at a predeterminedpower factor of unity, leading or lagging in any particular case.

The foregoing relationship between the traveling stator magnetic waveand the fixed flux field produced by field means 14 may be seen moreparticularly by reference to FIG. 5. The traveling flux field of statormeans 12 is indicated by curve 54 and the fixed flux field indicated bycurve 56 produce a resultant wave 58. The propulsive thrust or force Tis determined according to the relationship: I

.T equals k0,F sin delta,,

Wherein T equals thrust, 9, designates the amplitude of the resultantwave 58, F equals the magnetomotive force of field wave 56, and 8, isthe displacement angles between the resultant flux 0, and the fieldmagnetometive force f which is essentially constant and slightly lessthan 90 electrical degrees. The foregoing relationship results whenstator wave 54 and field wave 56 are maintained substantially stationaryrelative to each other.

The magnetomotive force. andthe resultant flux 0,

are directly related to field voltage E, and stator terminal voltage V,.Thus, the displacement angle 8,, is maintained substantially constant atany speed or frequency. This condition holds true at the zero orstarting condition of motorl0 as well as at any relative movementbetween'rotor l6 and stator means 12. In the starting condition, thefrequency is reduced to zero. At zero Jspeed commutator 46 senses thespeed and position of rotor 16 while a polyphase current input tofrequency converter 48 occurs. The stator current distribution and,magnetic wave 54 along the air gap of the stator is approximatelysinusoidal and displaced in space from the field magnetic wave 56 byapproximately .90 electrical degrees (or other selected angle). At zerospeed, stator 54 and field wave 56 are again stationary'with respect toeach other and separated by a plied. to field windings 28. The separatesource for energizing field windings 28 is suggested in FIG. 7 byreference numeral 52.

Referring to FIG. 2,- the inventive principles'and structures discussedabove and shown in FIG. .1, for example, may byseenincorporated inpropulsion means as shown in FIGS. 2 and 3.. The stated propulsion meansillustratively comprise an annular housing of suitable low resistancehydrodynamic shape having a leading edge 72 and a trailing edge 74 andaffixed to a pivotally movable shaft 76. A propeller 78 is'rotatableabout an axis of rotation through the lo'gnitu'dinal center of propellershaft 80 operatively connected to bearing supports 82 at each end of theshaft. Bearing supports 82 are mounted in stationary relationship withhousing 70 by means of two or more struts 84 as suggested by FIG. 2.Each of the blade tips of propeller 78 is permanently affixed tosubstantially cylindrical rotor element 16 at suitable locations such asby securing the stator blades to rigid mounting ring 40 which in turn issecured to the interdigitated salient magnet projections of the rotor.Stator means 12 and field means 14 are not cylindrical, but segments ofacylinder, and two separate units are situated at diametrically oppositelocations about rotor 16 and in spaced relationship therewith in theillustrative embodiment of FIG. 2, the operational relationship betweenitems l2, l4, and 16 shown in FIG. 2 being identical withthe'corresponding items discussed hereinabove in connection with FIG. 1.However, in the embodiment shown by FIG. 2, stator means 12 and fieldmeans 14, together with their variwater-impervious coating 88 assuggested in FIG. 2. Plastic 86, for example, may comprisestyrofoam orcellular type plastic, while coating 88. may comprise required inconventional inboardv motor boats is required for shaft 80 ll'l'flfiScase, since the shaft does not penetrate the hull. Moreover, it may beseen that directional control is provided in the structure shown.

by FIGS. 2 and 3 by rotation of shaft 76 even without any forwardmovement of boat 90 such as would'other-f wise be required in mostrudder installations. Also,

where high power is required in any case, additional seg-mental modularunits of stator and field-coil means 12 and 14 may be used instead ofonly two.

The embodiment shown herein is characterized by uniformly high startingtorque'and sustained motive power. In thisembodiment, additionalsegmented or modular units of stator and field winding means 12 and 14may be conveniently employed instead of merely one or two as shownin thedrawings. Illustratively, each segment may comprise about 10 to 20 ofthe total 360 circle defined by rotor 16 in any case, and a single suchsegment is sufficient for power applications of moderate demand. Inaddition to its versatility with regard to power output, the designparticularly shown by FIGS. 2 and 3 is especially advantageous as ameans for propelling troop transports and warships. Thus, theelimination of gear noise eliminates most of the danger of detection byenemy submarines'or impact by. torpedoes and the like which depend forsearch or guidance accuracy upon sonar or other sound-sensing and homingsystems. As applied to deep submergence vehicles, the propulsion systemshown in FIG. 2, for example, is without operational limits with regardto depth, since no seals are required between a hull and a rotatingshaft as with conventional submarines and torpedoes, for example. Thus,extremely high differential pressures may exist between the inside andoutside areas of a submerged hull, without producing any of the lsealing problems associated with shaft penetration through a hull whenthe inventive concept of this case is employed. Moreover, the noise,vibration and shock loads associated with large power plants, huge geartrains and long propeller drive shafts in modern passenger ships,especially those effects occurring in heavy seas when the shipspropeller is periodically elevated out of the water between waves, wouldbe very considerably reduced where the drive system shown in FIG. 2 ofthe accompanying drawings is used.

I claim 1. Gearless drive means comprising:

a linear synchronous motor having a generally cylindrical interdigitatedrotor, bearing support means for supporting said rotor rotationallyabout an axis, said motor further having stator means,

said motor also having field pole means operatively associated with saidstator means,

mounting means for supporting said stator means and said field polemeans stationary relatively to said rotor, and

propulsion means secured to said rotor and rotatable therewith forpropelling said motor along a path of travel, said propulsion meansconsisting of a marine propeller having a plurality of blades joinedv tosaid rotor at the tips thereof, said propeller being rotatable about thesame rotation axis as said rotor.

2. A propeller drive system for boats, consisting essentially of: p

a generally cylindrical water-impervious housing,

means connecting said housing to a boat,

a marine propeller axially centered within said housing, said propellerhaving a plurality of blades,

an interdigitated metallic rotor secured to the outer tips of saidblades, said rotor having a plurality of substantially parallel spacedapart elongate magnetic projections,

segmented stator coil means mounted within said housing and operativelyrelated with said rotor to produce a traveling magnetic wave in saidrotor,

segmented field coil means mounted within said housing and operativelyrelated to produce a stationary magnetic wave in said rotor,

bearing support means connected to said housing for supporting saidpropeller rotationally relative to said housing and with said rotorspaced-apart from and in close juxtaposition with said housing, and

electrical power connection means for supplying said stator coil meanswith electrical current of predetermined frequency.

1. Gearless drive means comprising: a linear synchronous motor having agenerally cylindrical interdigitated rotor, bearing support means forsupporting said rotor rotationally about an axis, said motor furtherhaving stator means, said motor also having field pole means operativelyassociated with said stator means, mounting means for supporting saidstator means and said field pole means stationary relatively to saidrotor, and propulsion means secured to said rotor and rotatabletherewith for propelling said motor along a path of travel, saidpropulsion means consisting of a marine propeller having a plurality ofblades joined to said rotor at the tips thereof, said propeller beingrotatable about the same rotation axis as said rotor.
 2. A propellerdrive system for boats, consisting essentially of: a generallycylindrical water-impervious housing, means connecting said housing to aboat, a marine propeller axially centered within said housing, saidpropeller having a plurality of blades, an interdigitated metallic rotorsecured to the outer tips of said blades, said rotor having a pluralityof substantially parallel spaced apart elongate magnetic projections,segmented stator coil means mounted within said housing and operativelyrelated with said rotor to produce a traveling magnetic wave in saidrotor, segmented field coil means mounted within said housing andoperatively related to produce a stationary magnetic wave in said rotor,bearing support means connected to said housing for supporting saidpropeller rotationally relative to said housing and with said rotorspaced-apart from and in close juxtaposition with said housing, andelectrical power connection means for supplying said stator coil meanswith electrical current of predetermined frequency.